1. Field of the Invention
The present invention relates in general to a non-volatile ferroelectric memory device having a sensing voltage control function, and more particularly, to a non-volatile ferroelectric memory device, wherein a sense amp compensates a sensing voltage difference in a main bit line caused by a temperature change, thereby obtaining a stable data sensing.
2. Description of the Related Art
In general, a non-volatile ferroelectric memory, i.e., a FeRAM (Ferroelectric Random Access Memory), has a data processing speed equal to that of a DRAM (Dynamic Random Access Memory) and also is capable of preserving stored data even when the power is off. The FeRAM and DRAM are memory devices with similar structures, but the FeRAM uses a capacitor made of a ferroelectric material to benefit a high residual polarization characteristic of the ferroelectric material. The residual polarization of the ferroelectric capacitor allows data to be maintained in an FeRAM memory cell and not erased even if an electric field applied to the memory cell is removed.
The general techniques and ideas associated with the above-described FeRAM have been already disclosed in Korean Patent Application No. 1998-14400 applied by the same inventor. Therefore, basic structure and operational principles of the FeRAM will not be further discussed here.
However, as the operational voltage of a chip of the FeRAM is getting lower, a sensing voltage of a cell is also reduced. In effect, this caused much difficulty in obtaining a high-speed operation in a circuit having a 1T1C (1-Transistor 1-Capacitor) structure.
Especially when the sensing voltage of a cell data is low, a voltage margin for sensing timing is reduced. Therefore, if a temperature change in a memory is great, a bit line sensing voltage fluctuates greatly. In other words, when the temperature change in a memory is great, it is very difficult to detect the sensing voltage of a bit line using a fixed sensing threshold voltage.